Nano-scale electrical contacts, memory devices including nano-scale electrical contacts, and related structures and devices

ABSTRACT

Electrical contacts may be formed by forming dielectric liners along sidewalls of a dielectric structure, forming sacrificial liners over and transverse to the dielectric liners along sidewalls of a sacrificial structure, selectively removing portions of the dielectric liners at intersections of the dielectric liners and sacrificial liners to form pores, and at least partially filling the pores with a conductive material. Nano-scale pores may be formed by similar methods. Bottom electrodes may be formed and electrical contacts may be structurally and electrically coupled to the bottom electrodes to form memory devices. Nano-scale electrical contacts may have a rectangular cross-section of a first width and a second width, each width less than about 20 nm. Memory devices may include bottom electrodes, electrical contacts having a cross-sectional area less than about 150 nm 2  over and electrically coupled to the bottom electrodes, and a cell material over the electrical contacts.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional of U.S. patent application Ser. No.13/547,228, filed Jul. 12, 2012, now U.S. Pat. No. 8,877,628, issuedNov. 4, 2014, the disclosure of which is hereby incorporated herein inits entirety by this reference.

TECHNICAL FIELD

Embodiments of the present disclosure relate to methods of forming poresand electrical contacts at a nano-scale (i.e., less than about 20 nm),as well as pores, electrical contacts, and memory devices formed by suchmethods.

BACKGROUND

Semiconductor structures are structures that are used or formed in thefabrication of semiconductor devices. Semiconductor devices include, forexample, electronic signal processors, electronic memory devices,photoactive devices, and microelectromechanical (MEM) devices. Suchstructures and materials often include one or more semiconductormaterials (e.g., silicon, germanium, a III-V semiconductor material,etc.), and may include at least a portion of an integrated circuit.

There are many types of electronic memory devices being used or underdevelopment. For example, dynamic random-access memory (DRAM) and NANDFlash memory have been used for many years. Other memory types, oftenreferred to as “emerging memory,” are currently under development andmay replace or supplement DRAM and NAND Flash memories as they becometechnologically and economically feasible. Some example emerging memorytypes include resistive random-access memory (RRAM), phase change memory(PCM), and magnetoresistive random-access memory (MRAM).

Some emerging memory types require relatively high electrical currentdensity (measured in amperes per unit area) to properly write, read,and/or erase data to memory cells thereof. The relatively highelectrical current density requires a relatively large amount ofelectrical current for proper operation. In addition, the large amountof current requires memory cell access devices (e.g., transistors,diodes) to be formed of a sufficient size to handle such electricalcurrents without failure.

In one known PCM configuration, an electrical contact having a thicknessof about 7.5 nm is formed by depositing a metal on a sidewall of astructure. The metal is then patterned by photolithography techniques toform the electrical contact having a cross-section of about 7.5 nm(defined by the thickness of the metal) by about 22 nm (defined by thephotolithography). A top portion of the electrical contact is recessed,and PCM cell material is introduced into the recess using a chemicalvapor deposition (CVD) process.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A through 7C illustrate a method of forming a pore, an electricalcontact, and a memory device according to embodiments of the presentdisclosure.

FIG. 1A illustrates a top view of a semiconductor structure according toan embodiment of the present disclosure, the semiconductor structureincluding a dielectric material, bottom electrodes formed in thedielectric material, a first dielectric structure formed over thedielectric material and over portions of the bottom electrodes, and afirst liner formed along sidewalls of the first dielectric structure.

FIG. 1B illustrates a cross-sectional side view of the semiconductorstructure of FIG. 1A taken at section line 1B-1B of FIG. 1A, furthershowing a substrate over which the dielectric material is formed.

FIG. 1C illustrates a cross-sectional side view of the semiconductorstructure of FIG. 1A taken at section line 1C-1C of FIG. 1A.

FIG. 2A illustrates a top view of the semiconductor structure of FIG. 1Aafter a first dielectric fill material has been formed over a surfacethereof.

FIG. 2B illustrates a cross-sectional side view of the semiconductorstructure of FIG. 2A taken at section line 2B-2B of FIG. 2A.

FIG. 2C illustrates a cross-sectional side view of the semiconductorstructure of FIG. 2A taken at section line 2C-2C of FIG. 2A.

FIG. 3A illustrates a top view of the semiconductor structure of FIG. 2Aafter a second dielectric structure has been formed over a surfacethereof and a second liner has been formed along sidewalls of the seconddielectric structure.

FIG. 3B illustrates a cross-sectional side view of the semiconductorstructure of FIG. 3A taken at section line 3B-3B of FIG. 3A.

FIG. 3C illustrates a cross-sectional side view of the semiconductorstructure of FIG. 3A taken at section line 3C-3C of FIG. 3A.

FIG. 4A illustrates a top view of the semiconductor structure of FIG. 3Aafter a second fill material has been formed over a surface thereof.

FIG. 4B illustrates a cross-sectional side view of the semiconductorstructure of FIG. 4A taken at section line 4B-4B of FIG. 4A.

FIG. 4C illustrates a cross-sectional side view of the semiconductorstructure of FIG. 4A taken at section line 4C-4C of FIG. 4A.

FIG. 5A illustrates a top view of the semiconductor structure of FIG. 4Aafter the second liner and portions of the first liner have been removedto form pores.

FIG. 5B illustrates a cross-sectional side view of the semiconductorstructure of FIG. 5A taken at section line 5B-5B of FIG. 5A.

FIG. 5C illustrates a cross-sectional side view of the semiconductorstructure of FIG. 5A taken at section line 5C-5C of FIG. 5A.

FIG. 6A illustrates a top view of the semiconductor structure of FIG. 5Aafter the pores have been filled with a conductive material to formelectrical contacts.

FIG. 6B illustrates a cross-sectional side view of the semiconductorstructure of FIG. 6A taken at section line 6B-6B of FIG. 6A.

FIG. 6C illustrates a cross-sectional side view of the semiconductorstructure of FIG. 6A taken at section line 6C-6C of FIG. 6A.

FIG. 7A illustrates a top view of the semiconductor structure of FIG. 6Aafter cell material and top electrodes have been formed and patternedover the electrical contacts.

FIG. 7B illustrates a cross-sectional side view of the semiconductorstructure of FIG. 7A taken at section line 7B-7B of FIG. 7A.

FIG. 7C illustrates a cross-sectional side view of the semiconductorstructure of FIG. 7A taken at section line 7C-7C of FIG. 7A.

FIG. 8 illustrates a simplified perspective view of an electricalcontact formed over an electrical feature according to an embodiment ofthe present disclosure.

FIG. 9 illustrates a simplified perspective view of a memory deviceaccording to an embodiment of the present disclosure including theelectrical contact of FIG. 8.

FIG. 10 is a simplified block diagram of a memory device according to anembodiment of the present disclosure.

FIG. 11 is a simplified block diagram of a system according to anembodiment of the present disclosure.

DETAILED DESCRIPTION

The following description provides specific details, such as materialtypes and processing conditions, in order to provide a thoroughdescription of embodiments of the present disclosure. However, a personof ordinary skill in the art will understand that the embodiments of thepresent disclosure may be practiced without employing these specificdetails. Indeed, the embodiments of the present disclosure may bepracticed in conjunction with conventional fabrication techniquesemployed in the semiconductor industry.

In addition, the description provided below does not describe a completeprocess flow for forming memory devices. The methods described below donot necessarily form complete semiconductor devices. The remainder ofthe process flow and memory devices are known to those of ordinary skillin the art. Accordingly, only the methods and devices necessary tounderstand embodiments of the present disclosure are described in detailherein. Additional acts to form complete memory devices and systems maybe performed by conventional fabrication techniques known to those ofordinary skill in the art.

As used herein, any relational term, such as “first,” “second,” “over,”“underlying,” “horizontal,” “vertical,” etc., is used for clarity andconvenience in understanding the present disclosure and accompanyingdrawings and does not connote or depend on any specific preference,orientation, or order, except where the context clearly indicatesotherwise.

As used herein, the term “substantially,” with reference to a givenparameter, property, or condition, means and includes to a degree thatone of ordinary skill in the art would understand that the givenparameter, property, or condition is met within a degree of variance,such as within acceptable manufacturing tolerances.

As used herein, the phrase “cross-section,” with reference to anelectrically conductive structure (e.g., an electrical contact), meansand includes a section taken substantially perpendicular to an averageelectrical current flow through the electrically conductive structureduring operation thereof.

As used herein, the term “nano-scale” means and includes at a scalebelow conventional photolithographic resolution limits. For example, anano-scale structure may have at least one dimension less than about 20nm. In some embodiments, the nano-scale structure may have at least onedimension that is less than about 10 nm. In some embodiments, thenano-scale structure may have cross-sectional dimensions in twotransverse (e.g., perpendicular) directions less than about 20 nm each,or less than about 10 nm each.

In the following detailed description, reference is made to theaccompanying drawings, which form a part of the present disclosure, andin which is shown, by way of illustration, specific embodiments in whichthe present disclosure may be practiced. These embodiments are describedin sufficient detail to enable a person of ordinary skill in the art topractice the present disclosure. However, other embodiments may beutilized and structural and compositional changes may be made withoutdeparting from the scope of the present disclosure. The illustrationspresented herein are not meant to be actual views of any particularsystem, device, or structure, but are merely idealized representationsthat are employed to describe the embodiments of the present disclosure.The drawings presented herein are not necessarily drawn to scale.Additionally, elements common or similar between drawings may retain thesame numerical designation.

The embodiments of the present disclosure include methods of formingnano-scale pores, methods of forming nano-scale electrical contacts, andmethods of forming memory devices and systems including such nano-scalepores and/or electrical contacts. The embodiments of the presentdisclosure also include nano-scale pores, nano-scale electricalcontacts, memory devices, and systems formed by such methods. Thenano-scale pores and electrical contacts of the present disclosure mayhave one or more cross-sectional dimensions below conventionalphotolithography resolution limits. In some embodiments, the nano-scalepores and electrical contacts may have two cross-sectional dimensions intwo transverse (e.g., perpendicular) dimensions that each have anano-scale value. Such nano-scale electrical contacts, when used inmemory devices, may effectively reduce the amount of electrical currentutilized to maintain a particular current density, and may enablesmaller access devices to be used.

FIG. 1A through 7C illustrate a method of forming pores, electricalcontacts, and memory devices in accordance with embodiments of thepresent disclosure. Such methods may be used to form apparatuses (e.g.,memory devices and systems, devices and systems including such memorydevices, etc.) including nano-scale electrical contacts. Although thedrawings of the present disclosure illustrate forming electricalcontacts configured to electrically couple bottom electrodes to cellmaterial of a memory device (e.g., a phase change memory (PCM) device ora resistive random-access memory (RRAM) device, etc.), such anapplication is presented by way of example only. Indeed, the methods andstructures of the present disclosure may be used in any applicationwhere a small (e.g., nano-scale) electrical contact or other structureis desired or even in applications where a relatively larger electricalcontact or other structure is desired.

FIGS. 1A through 1C illustrate various views of a semiconductorstructure that includes a substrate 100, a dielectric material 102 overthe substrate 100, bottom electrodes 104 over the substrate 100 and inthe dielectric material 102, a dielectric structure 106 over portions ofthe dielectric material 102 and optionally over portions of the bottomelectrodes 104, and dielectric liners 108 along sidewalls 107 of thedielectric structure 106. Portions of the bottom electrodes 104underlying the dielectric structure 106 and the dielectric liners 108are shown by dashed lines in FIG. 1A. The substrate 100 may comprise asemiconductor material, such as silicon, germanium, a III-Vsemiconductor material, etc. Although not shown for simplicity,electrical features, such as access devices (e.g., transistors, diodes,etc.), electrically conductive lines (e.g., digit lines, etc.), andelectrically conductive vias, may be formed in, on, above, or below thesubstrate 100. The electrical features may be formed in the substrate100 by conventional methods. However, in some embodiments, the physicalsize of one or more of the electrical features, such as the size of theaccess devices, may be reduced compared to conventional configurationsdue to a relatively lower electrical current required to effectivelyoperate memory cells to be formed including a smaller electrical contactsize, as will be described in more detail below. In addition, a densityof the access devices (i.e., a number of access devices per unit area)may be increased due to the reduced size of each access device.

To form the semiconductor structure, a dielectric material 102 may bedisposed over the substrate 100. By way of non-limiting example, thedielectric material 102 may comprise a silicon oxide material (e.g.,SiO₂) formed over the substrate 100 by one or more of a spin-coatingoperation, a chemical vapor deposition (CVD) operation, depositing theSiO₂ from a tetraethylorthosilicate (TEOS) precursor (i.e., a TEOSoperation), and an atomic layer deposition (ALD) operation, for example.

The bottom electrodes 104 may be formed over the substrate 100 and inthe dielectric material 102. Each bottom electrode 104 may be inelectrical contact with an access device (not shown) of the substrate100, either directly or indirectly (i.e., through another electricallyconductive feature). The bottom electrodes 104 may be formed byselectively removing material from the dielectric material 102 and byforming a conductive material in the area where material was removed.Material may be removed from the dielectric material 102 usingconventional material removal techniques, such as by photolithographicmasking and etching operations, as will be understood by one of ordinaryskill in the art. In such embodiments, a mask (not shown) having adesired pattern may be formed over the dielectric material 102, which isexposed and developed to form apertures in locations where the bottomelectrodes 104 are to be formed. Portions of the dielectric material 102that are exposed may be removed using an etching operation, such as adry (i.e., reactive ion) etching operation or a wet (i.e., chemical)etching operation, to form holes in the dielectric material. After theholes are at least partially formed, the mask may be removed. The holesmay be filled with an electrically conductive material to form thebottom electrodes 104 by conventional material formation techniques, aswill be understood by one of ordinary skill in the art. Conductivematerial may be formed in the holes using one or more of an electrolessplating operation, an electrolytic plating operation, an ALD operation,a CVD operation, a physical vapor deposition (PVD) operation, and asputtering operation, for example. The conductive material of the bottomelectrodes 104 may be selected to exhibit a high electricalconductivity. For example, the bottom electrodes 104 may comprise one ormore of tungsten, titanium, aluminum, copper, cobalt, and alloys of suchmaterials.

If conductive material used to form the bottom electrodes 104 is formedover an upper surface of the dielectric material 102 when viewed in theperspective of FIGS. 1B and 1C), the conductive material may be removedfrom the upper surface of the dielectric material 102. By way of exampleand not limitation, one or more of an etching operation, a grindingoperation, and a polishing operation (e.g., a chemical-mechanicalpolishing (CMP) operation) may be used to remove the conductive materialfrom the upper surface of the dielectric material 102. Such materialremoval operations may physically and electrically isolate adjacentbottom electrodes 104 from each other.

Although the bottom electrodes 104 are shown in FIG. 1A as beingsubstantially square in cross-section, the present disclosure is notlimited by the shape of the bottom electrodes 104. For example, in someembodiments, the bottom electrodes 104 may have a cross-section that isgenerally circular, rectangular, polygonal, or irregular.

After the bottom electrodes 104 are formed over the substrate 100 andthrough the dielectric material 102, the dielectric structure 106 may beformed over the dielectric material 102 and, optionally, over portionsof the bottom electrodes 104, as shown in FIGS. 1A and 1C. The materialof the dielectric structure 106 may be the same or a different materialcompared to the dielectric material 102, and may be formed over thedielectric material 102 by one or more of a spin-coating operation, aCVD operation, a TEOS operation, and an ALD operation, for example. Byway of example and not limitation, the dielectric structure 106 may beformed from one or more of a silicon oxide material, a silicon carbidematerial, a hafnium oxide material, an aluminum oxide material, and azirconium oxide material, for example. The dielectric structure 106 maybe in the form of a line or stripe of dielectric material longitudinallyextending in a first direction 110. A lateral width of the dielectricstructure 106 in a second direction 112 transverse (e.g., perpendicular)to the first direction 110 may, optionally, be selected to dispose thedielectric structure 106 over portions of adjacent bottom electrodes104. The lateral width of the dielectric structure 106 may definelocations where electrical contacts are to be formed over the bottomelectrodes 104, as will be explained in more detail below. Accordingly,the dielectric structure 106 may have sidewalls 107 positioned proximatelocations where electrical contacts are to be formed over the bottomelectrodes 104. The dielectric structure 106 may be formed by depositinga material over the dielectric material 102 and bottom electrodes 104and removing portions of the material that do not define the dielectricstructure 106. Material may be removed by conventional material removaltechniques, such as by one or more photolithographic masking and etchingoperations similar to those described above, to form the dielectricstructure 106 shown in FIGS. 1A and 1C.

The dielectric liners 108 may be formed along the sidewalk 107 of thedielectric structure 106. A dielectric material having etch selectivitywith respect to the dielectric structure 106 and/or the dielectricmaterial 102 may be deposited over the dielectric structure 106 and overexposed portions of the dielectric material 102 and bottom electrodes104. By way of example and not limitation, the dielectric liners 108 maybe formed of one or more of a nitride material and an oxide material.For example, the dielectric liners 108 may be formed of one or more ofsilicon nitride, aluminum oxide, hafnium silicate, zirconium silicate,hafnium oxide, and zirconium oxide. A conformal deposition technique maybe used to dispose the dielectric liners 108 along the sidewalk 107 ofthe dielectric structure 106. By way of example and not limitation, aCVD operation (e.g., a metallorganic CVD (MOCVD) operation) or an ALDoperation may be used. Material of the dielectric liners 108 notdisposed along the sidewalls 107 may be removed by an anisotropicmaterial removal operation, such as by an anisotropic dry reactive ionetching operation. Thus, material of the dielectric liners 108 may beremoved from over horizontal (when viewed from the perspective of FIGS.1B and 1C) surfaces of the dielectric material 102, the bottomelectrodes 104, and the dielectric structure 106, while material mayremain along the vertical (when viewed from the perspective of FIG. 1C)sidewalls 107 of the dielectric structure 106 to define the dielectricliner 108.

A thickness of the dielectric liners 108 in the second direction 112 mayultimately define one dimension of an electrical contact to be formedover the bottom electrodes 104, as will be explained in more detailbelow. Accordingly, the thickness of each dielectric liner 108 may betailored to a desired electrical contact dimension. By way of exampleand not limitation, the dielectric liner 108 may be formed to have anano-scale thickness, such as less than about 20 nm, to form anano-scale electrical contact. In some embodiments, the dielectric liner108 may have a thickness of less than about 10 nm. In some embodiments,the dielectric liner 108 may have a thickness of about 2 nm or less.

Referring to FIGS. 2A through 2C, a dielectric filler material 114 maybe formed over portions of the dielectric material 102 and bottomelectrodes 104 that are not covered by the dielectric structure 106 anddielectric liners 108. In other words, the dielectric filler material114 may be formed adjacent to the dielectric liners 108. In someembodiments, the dielectric filler material 114 may be the same as thematerial of the dielectric structure 106. The dielectric filler material114 may be formed by one or more of a spin-coating operation, a CVDoperation, a TEOS operation, and an ALD operation, for example. An uppersurface (when viewed from the perspective of FIG. 2C) of the dielectricfiller material 114, and optionally upper surfaces of the dielectricstructure 106 and the dielectric liners 108, may be planarized by, forexample, by one or more of an etching operation, a grinding operation,and a polishing operation (e.g., a CMP operation). The planarization ofthe dielectric filler material 114 may also remove any material over thedielectric liner 108 to expose the upper surface of the dielectricliners 108.

Referring to FIGS. 3A through 3C, a sacrificial structure 116 andsacrificial liners 118 may be formed to longitudinally extend in thesecond direction 112 (i.e., transverse to the first direction 110 inwhich the dielectric structure 106 longitudinally extends) over portionsof the dielectric structure 106, the dielectric liners 108, and thedielectric filler material 114. The sacrificial structure 116 and thesacrificial liners 118 are referred to as “sacrificial” because thesacrificial structure 116 and the sacrificial liners 118 may be removedin a subsequent operation, as will be explained in more detail below.

As described above with reference to the dielectric structure 106, alateral width of the sacrificial structure 116 in the first direction110 may, optionally, be selected to dispose the sacrificial structure116 over portions of adjacent bottom electrodes 104. The lateral widthof the sacrificial structure 116 may define locations where electricalcontacts are to be formed over the bottom electrodes 104, as will beexplained in more detail below. Accordingly, the sacrificial structure116 may have sidewalls 117 positioned proximate locations whereelectrical contacts are to be formed over the bottom electrodes 104. Thesacrificial structure 116 may be formed by depositing a material overthe dielectric structure 106, the dielectric liners 108, and thedielectric filler material 114 and removing portions of the materialthat do not define the sacrificial structure 116. Material may beremoved by conventional material removal techniques, such as by one ormore photolithographic masking and etching operations similar to thosedescribed above, to form the sacrificial structure 116 shown in FIGS. 3Aand 3B.

The sacrificial liners 118 may be formed along the sidewalls 117 of thesacrificial structure 116. A material having etch selectivity withrespect to the sacrificial structure 116, the dielectric structure 106,and/or the dielectric filler material 114 may be deposited over thesacrificial structure 116 and over exposed portions of the dielectricstructure 106, the dielectric liners 108, and the dielectric fillermaterial 114. The sacrificial liners 118 and the dielectric liners 108may be located to define intersections between the sacrificial liners118 and the dielectric liners 108 located over the bottom electrodes104. The sacrificial liners 118 may be formed of the same or a differentmaterial compared to the dielectric liners 108, as long as each of thesacrificial liners 118 and the dielectric liners 108 is selectivelyremovable with respect to the dielectric structure 106, dielectricfiller material 114, sacrificial structure 116, and a subsequentlyformed sacrificial filler material 120 (described below with referenceto FIGS. 4A through 4C). A conformal deposition technique may be used todispose the sacrificial liners 118 along the sidewalls 117 of thesacrificial structure 116. By way of example and not limitation, a CVDoperation (e.g., an MOCVD operation) or an ALD operation may be used.Material of the sacrificial liners 118 not disposed along the sidewalls117 may be removed by an anisotropic material removal operation, such asby an anisotropic dry reactive ion etching operation. Thus, material ofthe sacrificial liners 118 may be removed from over horizontal (whenviewed from the perspective of FIGS. 3B and 3C) surfaces of thedielectric structure 106, dielectric liners 108, dielectric fillermaterial 114, and sacrificial structure 116, while material may remainalong the vertical (when viewed from the perspective of FIG. 3B)sidewalls 117 of the sacrificial structure 116 to define the sacrificialliner 118.

A thickness of the sacrificial liners 118 taken in the first direction110 may ultimately define one dimension of an electrical contact to beformed over the bottom electrodes 104, as will be explained in moredetail below. Accordingly, the thickness of each sacrificial liner 118may be tailored to a desired electrical contact dimension. By way ofexample and not limitation, the sacrificial liner 118 may be formed tohave a nano-scale thickness, such as less than about 20 nm, to form anano-scale electrical contact. In some embodiments, the sacrificialliner 118 may have a thickness of less than about 10 nm. In someembodiments, the sacrificial liner 118 may have a thickness of about 2nm or less.

Referring to FIGS. 4A through 4C, a sacrificial filler material 120 maybe formed over portions of the dielectric structure 106, dielectricliners 108, and dielectric filler material 114 that are not covered bythe sacrificial structure 116 and sacrificial liners 118. In otherwords, the sacrificial filler material 120 may be formed adjacent to thesacrificial liners 118. The bottom electrodes 104, dielectric structure106, dielectric liners 108, and dielectric filler material 114 are shownin dashed lines in FIG. 4A because each of these structures andmaterials is covered by the sacrificial structure 116, sacrificialliners 118, and sacrificial filler material 120 when viewed from theperspective of FIG. 4A. In some embodiments, the sacrificial fillermaterial 120 may be the same as the material of the sacrificialstructure 116. The sacrificial filler material 120 may be formed by oneor more of a spin-coating operation, a CVD operation, a TEOS operation,and an ALD operation, for example. An upper surface (when viewed fromthe perspective of FIG. 4C) of the sacrificial filler material 120, andoptionally upper surfaces of the sacrificial structure 116 and thesacrificial liners 118, may be planarized by, for example, one or moreof an etching operation, a grinding operation, and a polishing operation(e.g., a CMP operation). The planarization of the sacrificial fillermaterial 120 may also remove any material over the sacrificial liners118 to expose the upper surface of the sacrificial liners 118.

Referring to FIGS. 5A through 5C, in conjunction with FIGS. 4A through4C, one or more material removal operations may be performed to removethe sacrificial liners 118 to form trenches 122 between the sacrificialstructure 116 and the sacrificial filler material 120, and to removeportions of the dielectric liners 108 underlying the trenches 122 toform pores 124. The portions of the dielectric liners 108 to be removedmay be defined by an intersection between the dielectric liners 108 andthe sacrificial liners 118. By way of non-limiting example, thesacrificial liners 118 and portions of the dielectric liners 108 may beremoved by one or more dry etch operations and/or wet etch operations.In embodiments where the dielectric liners 108 and the sacrificialliners 118 comprise the same material, or where the dielectric liners108 and the sacrificial liners 118 are otherwise removable by a similaretch chemistry, a single material removal operation may be performed.Alternatively, two or more material removal operations may be used tosequentially remove the sacrificial liners 118 to form the trenches 122and then remove the portions of the dielectric liners 108 underlying thetrenches 122 to form the pores 124. After the pores 124 are formed usingthe one or more material removal operations, the bottom electrodes 104may be exposed through the pores 124.

The lateral width of the trenches 122 in the first direction 110 may beultimately defined by the thickness of the sacrificial liners 118 priorto removal thereof. Accordingly, the pores 124 formed through andunderlying the trenches 122 may each have a first width A in the firstdirection 110 defined by the thickness of the sacrificial liners 118prior to removal thereof. Similarly, the pores 124 may have a secondwidth B in the second direction 112 ultimately defined by the thicknessof the dielectric liners 108. Thus, as shown in FIG. 5A, the pores 124may each have a generally rectangular (e.g., substantially square)cross-section of the first width A in the first direction 110 and of thesecond width B in the second direction 112. The first width A may beselected by forming the sacrificial liners 118 to have a desiredthickness, as described above, of the first width A. The second width Bmay be independently selected by forming the dielectric liners 108 tohave a desired thickness, as described above, of the second width B.Accordingly, a cross-sectional shape and size of the pores 124 may betailored by selecting the thicknesses of the dielectric liners 108 andthe sacrificial liners 118. Thus, the pores 124 may be formedindependently of photolithography resolution limits. As described above,one or both of the dielectric liners 108 and the sacrificial liners 118may have a nano-scale thickness. As a result, one or both of the firstwidth A and the second width B may have a nano-scale value. By way ofexample and not limitation, one or both of the first width A and thesecond width B of the pores 124 may be less than about 20 nm. In someembodiments, one or both of the first width A and the second width B ofthe pores 124 may be less than about 10 nm. In some embodiments, one orboth of the first width A and the second width B of the pores 124 may beabout 2 nm or less.

Accordingly, the present disclosure includes methods of formingnano-scale pores. According to such methods, a first structure may beformed to longitudinally extend in a first direction. A first linerhaving a nano-scale thickness may be formed along a sidewall of thefirst structure, and a first filler material may be formed adjacent tothe first liner. A second structure may be formed over the firststructure, the first liner, and the first filler material, the secondstructure longitudinally extending in a second direction transverse tothe first direction. The method may also include forming a second linerhaving a nano-scale thickness along a sidewall of the second structureand forming a second filler material adjacent to the second liner. Thesecond liner may be removed to form a trench between the secondstructure and the second filler material. A portion of the first linerexposed through the trench may be removed to form a nano-scale pore.

Referring to FIGS. 6A through 6C, in conjunction with FIGS. 5A through5C, the pores 124, and optionally the trenches 122, may be at leastpartially filled with a conductive material, such as one or more oftungsten, titanium, aluminum, copper, cobalt, and alloys of suchmaterials, for example. By way of example and not limitation, the pores124 and the trenches 122 may be filled with a conductive material by atleast one of an electroless plating operation, an electrolytic platingoperation, an ALD operation, a CVD operation, a PVD operation, and asputtering operation. A multi-step operation may be used, such asforming a seed layer then growing another conductive material on theseed layer. The conductive material may be electrically coupled with thebottom electrodes 104 at the bottom of each pore 124.

After the pores 124 are sufficiently filled with a conductive material,the sacrificial structure 116, sacrificial filler material 120, andconductive material in the trenches 122 may be removed, such that theconductive material remains in the pores 124 to form electrical contacts126. The sacrificial structure 116, sacrificial filler material 120, andconductive material in the trenches 122 may be removed by one or morematerial removal operations, such as, for example, a chemical etchingoperation, a grinding operation, and a polishing operation (e.g., a CMPoperation). In some embodiments, one or more of the dielectric structure106, remaining portions of the dielectric liner 108, dielectric fillermaterial 114, and bottom electrodes 104 may function as an etch-stopmaterial or CMP-stop material to assist in controlling the depth atwhich material is removed. Alternatively, or in addition, a separateetch-stop layer or a separate CMP-stop layer (not shown) may have beenpreviously formed over the dielectric structure 106, the dielectricliner 108, and/or the dielectric filler material 114. Other methods ofremoving material to a desired depth that may be used in the formationof the electrical contacts 126 are known and, therefore, are notdescribed in detail in the present disclosure.

The electrical contacts 126 may each have a cross-section ultimatelydefined by an intersection between the dielectric liner 108 and thesacrificial liner 118 (FIGS. 3A and 4A). Accordingly, a first width C ofeach electrical contact 126 in the first direction 110 may be ultimatelydefined by the thickness of the sacrificial liners 118 prior to removalthereof. Similarly, the electrical contacts 126 may each have a secondwidth D in the second direction 112 ultimately defined by the thicknessof the dielectric liners 108. Thus, as shown in FIG. 6A, the electricalcontacts 126 may each have a generally rectangular (e.g., substantiallysquare) cross-section of the first width C in the first direction 110and of the second width D in the second direction 112. The first width Cmay be selected by forming the sacrificial liners 118 to have a desiredthickness, as described above, of the first width C. The second width Dmay be independently selected by forming the dielectric liners 108 tohave a desired thickness, as described above, of the second width D.Accordingly, a cross-sectional shape and size of each electrical contact126 may be tailored by selecting the thicknesses of the dielectricliners 108 and the sacrificial liners 118. As described above, one orboth of the dielectric liners 108 and the sacrificial liners 118 mayhave a nano-scale thickness. As a result, one or both of the first widthC and the second width D may have a nano-scale value. By way of exampleand not limitation, one or both of the first width C and the secondwidth D of the electrical contacts 126 may be less than about 20 nm. Insome embodiments, one or both of the first width C and the second widthof the electrical contacts 126 may be less than about 10 nm. In someembodiments, one or both of the first width C and the second width D ofthe electrical contacts 126 may be about 2 nm or less. Alignment of theelectrical contacts 126 having such nano-scale widths to the underlyingbottom electrodes 104 may be simplified due to a greater margin aroundthe electrical contacts 126 in both the first direction 110 and thesecond direction 112 compared to electrical contacts that are notnano-scale in the first direction 110 and the second direction 112.

By selecting the first width C and the second width D, a desiredcross-sectional area of each of the electrical contact 126 may beobtained. The cross-sectional area may, in some embodiments, be smallerthan is currently obtainable through conventional photolithographictechniques. The electrical contacts 126 may each have a cross-sectionalarea of less than about 150 nm², less than about 100 nm², less thanabout 50 nm², or less than about 10 nm², for example. Thus, thecross-sectional area of each of the electrical contacts 126 isdetermined by the thicknesses of the dielectric liners 108 and thesacrificial liners 118. In some embodiments, the cross-sectional area ofthe electrical contact 126 may be about 4 nm². Certain memory typesrequire a minimum current density, expressed in amperes per unit of area(e.g., amperes per square meter), to function properly. Reducing thearea through which current flows, such as by reducing thecross-sectional area of the electrical contacts 126, may enable thecurrent flowing through each memory cell to be proportionally reduced.Therefore, overall current requirements and power consumption canlikewise be reduced for a given number of memory cells formed with therelatively smaller electrical contacts 126.

In addition to enabling the formation of relatively smaller electricalcontacts 126 than is possible through conventional photolithography,controllability and uniformity of the electrical contacts 126 may beimproved compared to structures formed by conventional photolithography.For example, when conventional photolithography is used to formstructures that approach, reach, or exceed the resolution limits ofconventional photolithography, there may be a relatively highvariability in the dimensions thereof. However, in the presentdisclosure, the dimensions of the electrical contacts 126 may beultimately dependent on the film thickness of the dielectric liners 108and of the sacrificial liners 118. Film thicknesses are more easilycontrollable (i.e., may exhibit less variability) at sizes nearphotolithographic resolution limits compared to feature dimensionsformed using conventional photolithography. Accordingly, the methods ofthe present disclosure may be used to form electrical contacts 126 thatare both more uniform and smaller compared to electrical contacts formedby conventional photolithography. These improvements can be realized indimensions of the electrical contacts 126 in both the first direction110 and the second direction 112.

Accordingly, a method of forming electrical contacts of the presentdisclosure may include forming dielectric liners along sidewalls of adielectric structure, forming sacrificial liners over and transverse tothe dielectric liners along sidewalls of a sacrificial structure todefine intersections where the sacrificial liners cross the dielectricliners, selectively removing portions of the dielectric liners at theintersections to form pores, and at least partially filling the poreswith a conductive material to form electrical contacts. One or both ofthe dielectric liners and the sacrificial liners may be formed to havenano-scale thicknesses.

Referring to FIGS. 7A through 7C, a cell material 128 and top electrodes130 may be sequentially formed over the electrical contacts 126 to forma plurality of memory cells. The composition of the cell material 128used to form the plurality of memory cells is dependent on the type ofmemory being formed. Some example memory types that may benefit fromcomprising the relatively small electrical contacts 126 of the presentdisclosure include: magnetoresistive random-access memory (MRAM),spin-transfer torque random-access memory (STT-RAM), phase change memory(PCM), conductive bridge RAM, and resistive random-access memory (RRAM).By way of example and not limitation, cell materials for RRAM maycomprise one or more of: a mixture of copper and molybdenum oxide;titanium and so-called “PCMO” (a compound of praseodymium, calcium,manganese, and oxygen); gold or platinum and a mixture of niobium andstrontium-titanium-oxide; strontium oxide and a mixture of niobium andstrontium-titanium-oxide; iron oxide; tantalum oxide; vanadium oxide;silver and a compound of lanthanum, calcium, manganese, and oxygen;copper and a mixture of chromium and strontium zirconates; achalcogenide material; and a perovskite material. The top electrodes 130may comprise an electrically conductive material, such as one or more oftungsten, titanium, aluminum, copper, cobalt, and mixtures and alloys ofsuch materials, for example. The cell material 128 may be electricallycoupled with the electrical contacts 126, and the top electrodes 130 maybe electrically coupled with the cell material 128.

The top electrodes 130 may be patterned to isolate digit lines 132adjacent to each other in the first direction 110 using conventionalmaterial removal techniques, such as by photolithographic masking andetching operations, as described above. Openings 134 may be formed toisolate the adjacent digit lines 132. As shown in FIGS. 7A and 7B, theopenings 134 may, optionally (depending on the electrical properties ofthe materials in the structure and the type of memory to be formed),extend into the semiconductor structure to isolate portions of the cellmaterial 128, dielectric structure 106, dielectric liner 108, anddielectric fill material 114. However, in other embodiments (not shown),some portions of the semiconductor structure may not be isolated fromadjacent portions or may be isolated further from adjacent portions whencompared to the embodiment shown in FIGS. 7A through 7C. For example,some memory types (e.g., oxide-based RRAM) may include an isolationtrench only extending into the structure to isolate the digit lines,while the cell material 128 may be left as a bulk material without anyisolation between adjacent digit lines. By way of another example, othermemory types (e.g., PCM) may include cell material 128 in each memorycell that is isolated from cell material 128 in adjacent memory cells inboth the first direction 110 and the second direction 112. Therefore,the present disclosure is not limited by the specific materials and/orconfigurations of the openings 134, cell material 128, and topelectrodes 130.

In some embodiments, the electrical contacts 126 may be used asso-called “heaters” for PCM types. In such embodiments, a state of a PCMcell may be changed by heating an associated electrical contact 126 tocause the cell material 128 of the PCM cell to change phase.

Accordingly, the present disclosure includes methods of forming memorydevices including forming bottom electrodes in a dielectric material andforming first liners over the bottom electrodes and the dielectricmaterials, the first liners extending in a first direction. The methodsmay also include forming second liners over the first liners, the secondliners extending in a second direction transverse to the firstdirection. The second liners may be removed to form trenches and toexpose portions of the first liners. Exposed portions of the firstliners may be removed to form pores over the bottom electrodes.Electrical contacts may be structurally and electrically coupled to thebottom electrodes in the pores. A cell material may be formed over andelectrically coupled to the electrical contacts. A conductive materialmay be formed over and electrically coupled to the cell material.

Referring to FIG. 8, an electrical contact 250 of the present disclosuremay be structurally and electrically coupled with a conductive feature252, such as an electrode, a contact pad, a conductive line, etc.Although the conductive feature 252 is shown in FIG. 8 as having agenerally circular cross-section, the conductive feature 252 may haveany convenient shape, such as rectangular, square, etc. In someembodiments, the conductive feature 252 may be formed by conventionalphotolithography techniques, and, therefore, may have cross-sectionaldimensions at or above conventional photolithographic resolution limits,such as greater than about 20 nm, for example. The electrical contact250 may have a generally rectangular (e.g., substantially square)cross-section defined by a first width E in a first direction and asecond width F in a second direction transverse (e.g., perpendicular) tothe first direction. One or both of the first width E and the secondwidth F may have nano-scale values, such as less than about 20 nm each.In some embodiments, one or both of the first width E and the secondwidth F may be less than about 10 nm. In some embodiments, one or bothof the first width F and the second width F may be about 2 nm or less.The cross-sectional area of the electrical contact 250 may be less thanabout 150 nm², less than about 100 nm², less than about 50 nm², or lessthan about 10 nm², for example. In some embodiments, the cross-sectionalarea of the electrical contact 250 may be about 4 nm². The electricalcontact 250 may be formed by the methods described above with referenceto FIGS. 1A through 6C.

Accordingly, the present disclosure includes nano-scale electricalcontacts comprising a conductive material having a rectangularcross-section comprising a first width in a first direction and a secondwidth in a second direction perpendicular to the first direction. Eachof the first width and the second width may be less than about 20 nm.The cross-section may have an area of less than about 150 nm². In someembodiments, each of the first width and the second width may be about 2nm or less.

Referring to FIG. 9, a memory device 260 of the present disclosure mayinclude the conductive feature 252 in the form of a bottom electrode andthe electrical contact 250, as described above with reference to FIG. 8.The memory device 260 may also include a cell material 262 structurallyand electrically coupled to the electrical contact 250 at an end thereofopposite the conductive feature 252, and another conductive feature 264in the form of a top electrode structurally and electrically coupled tothe cell material 262 on a side thereof opposite the electrical contact250. The memory device 260 may be formed by the methods described abovewith reference to FIGS. 1A through 7C.

Referring to FIG. 10, illustrated is a simplified block diagram of amemory device 500 implemented according to one or more embodimentsdescribed herein. The memory device 500 includes a memory array 502 anda control logic component 504. The memory array 502 may include aplurality of electrical contacts 126 and/or 250, as described above. Thecontrol logic component 504 may be configured to operatively interactwith the memory array 502 so as to read, write, or refresh any or allmemory cells within the memory array 502 through the electrical contacts126 and/or 250.

Accordingly, the present disclosure includes a memory device comprisingbottom electrodes in a dielectric material with nano-scale electricalcontacts over and electrically coupled to respective bottom electrodes.The nano-scale electrical contacts may each comprise a rectangularcross-section having an area less than about 150 nm². Cell material maybe over and electrically coupled to respective nano-scale electricalcontacts.

With reference to FIG. 11, illustrated is a simplified block diagram ofa system 600 implemented according to one or more embodiments describedherein. The system 600 includes at least one input device 602. The inputdevice 602 may be a keyboard, a mouse, or a touch screen. The system 600further includes at least one output device 604. The output device 604may be a monitor, touch screen, or speaker, for example. The inputdevice 602 and the output device 604 are not necessarily separable fromone another. The system 600 further includes a storage device 606. Theinput device 602, output device 604, and storage device 606 are coupledto a conventional processor 608. The system 600 further includes amemory device 610 coupled to the processor 608. The memory device 610may include at least one memory array according to one or moreembodiments described herein. The system 600 may be incorporated withina computing, processing, industrial, or consumer product. For example,without limitation, the system 600 may be included within a personalcomputer, a hand-held device, a camera, a phone, a wireless device, adisplay, a chip set, a game, a vehicle, or another known system.

Accordingly, a system is disclosed comprising a memory array including aplurality of nano-scale electrical contacts. Each nano-scale electricalcontact of the plurality of nano-scale electrical contacts may have asubstantially rectangular cross-sectional area of less than 150 nm².

While the present disclosure is susceptible to various modifications andalternative forms, specific embodiments have been shown by way ofexample in the figures and have been described in detail herein.However, the present disclosure is not intended to be limited to theparticular forms disclosed. Rather, the disclosure encompasses allmodifications, combinations, equivalents, and alternatives fallingwithin the scope defined by the following appended claims and theirlegal equivalents.

What is claimed is:
 1. A nano-scale electrical contact, comprising: aconductive material having a uniform rectangular cross-section along alength thereof, the uniform rectangular cross-section comprising a firstwidth in a first direction and a second width in a second directionperpendicular to the first direction, wherein each of the first widthand the second width is less than about 10 nm; a first dielectricmaterial adjacent to and in contact with the conductive material; and asecond dielectric material adjacent to and in contact with theconductive material, the second dielectric material different from thefirst dielectric material.
 2. The nano-scale electrical contact of claim1, wherein each of the first width and the second width is about 2 nm orless.
 3. A memory device, comprising: bottom electrodes in a dielectricmaterial; nano-scale electrical contacts over and electrically coupledto respective bottom electrodes, each of the nano-scale electricalcontacts comprising a conductive material having a uniform rectangularcross-section along a length thereof, the uniform rectangularcross-section comprising a first width in a first direction and a secondwidth in a second direction perpendicular to the first direction,wherein each of the first width and the second width is less than about10 nm; volumes of a first dielectric material adjacent to and in contactwith respective nano-scale electrical contacts; and at least one volumeof a second dielectric material adjacent to and in contact with thenano-scale electrical contacts, the second dielectric material differentfrom the first dielectric material; and cell material over andelectrically coupled to respective nano-scale electrical contacts. 4.The memory device of claim 3, further comprising top electrodes formedover and electrically coupled to the cell material.
 5. The memory deviceof claim 3, further comprising a substrate comprising a semiconductormaterial and access devices, wherein the bottom electrodes are formedover the substrate and are electrically coupled to respective accessdevices of the substrate.
 6. The memory device of claim 3, wherein thecell material comprises cell material of a memory type selected from thegroup consisting of magnetoresistive random-access memory, spin-transfertorque random-access memory, phase change memory, conductive bridgerandom-access memory and resistive random-access memory.
 7. The memorydevice of claim 3, wherein the cell material is selected from the groupconsisting of: copper and molybdenum oxide; titanium, praseodymium,calcium, manganese, and oxygen; niobium, strontium-titanium-oxide, andat least one of gold or platinum; strontium oxide, niobium, andstrontium-titanium-oxide; iron oxide; tantalum oxide; vanadium oxide;silver, lanthanum, calcium, manganese, and oxygen; copper, chromium, andstrontium zirconates; a chalcogenide material; and a perovskitematerial.
 8. The memory device of claim 3, wherein each of the firstwidth and the second width is about 2 nm or less.
 9. The memory deviceof claim 4, wherein the top electrodes comprise digit lines.
 10. Thememory device of claim 3, wherein the nano-scale electrical contactscomprise heaters and the cell material comprises a phase change cellmaterial.
 11. The memory device of claim 3, wherein the nano-scaleelectrical contacts comprise one or more of tungsten, titanium,aluminum, copper, cobalt, and alloys of tungsten, titanium, aluminum,copper, and cobalt.
 12. The nano-scale electrical contact of claim 1,wherein the nano-scale electrical contact comprises a heater for a phasechange memory cell material.
 13. The nano-scale electrical contact ofclaim 1, wherein the conductive material is selected from the groupconsisting of tungsten, titanium, aluminum, copper, cobalt, and alloysof tungsten, titanium, aluminum, copper, and cobalt.
 14. The nano-scaleelectrical contact of claim 1, wherein the conductive material ispositioned over and electrically coupled to an electrode of a memorydevice.
 15. The nano-scale electrical contact of claim 1, wherein thenano-scale electrical contact is electrically coupled to a memory cellmaterial.
 16. The nano-scale electrical contact of claim 1, whereinlateral sides of the conductive material are surrounded by a dielectricmaterial.
 17. A nano-scale electrical contact, comprising: a conductivematerial having a rectangular cross-section comprising a first width ina first direction and a second width in a second direction perpendicularto the first direction, wherein each of the first width and the secondwidth is about 2 nm or less; a first dielectric material adjacent to andin contact with the conductive material; and a second dielectricmaterial adjacent to and in contact with the conductive material, thesecond dielectric material exhibiting an etch selectivity with respectto the first dielectric material.